To keep it very simple,

Here is some of the research.

Here are some of the highlights of the article.

Journal of Arboriculture 9(12): December 1983


by Alex L. Shigo and Walter C. Shortle

Abstract. Many materials were used in and on experimentally inflicted wounds in many studies over a 13-year period. No material prevented decay. The individual tree had a greater effect on the wound than the treatments. Some individual trees of a species closed and compartmentalized wounds rapidly and effectively, regardless of treatment, while other trees did not close and compartmentalize treated or control wounds. The width of healthy wood behind wounds in red maple was the major factor affecting the course of the wound. Results are given from wounds on 275 treated and dissected trees.

Tree wound dressings do not prevent decay (Collins 1934, Marshall 1950, Shigo and Wilson 1977, Mercer 1979, 1982, Bonneman 1979, Dooley 1980), and are of limited benefit for wound closure (Neely 1970, McQuilkin 1950, Young and Tilford 1937).

Many arborists have known this for a long time. Results of research on wound dressings by many investigators during the last decade have further convinced these arborists, and they have stopped using wound dressings, or have discussed the treatment with their clients. Some arborists in this group - we will call them Group I - may paint wounds for cosmetic reasons, if the client still wants it done. Others in Group I refuse to paint wounds because they believe it reflects poorly on their professionalism.

Group II is arborists that doubt the worth of dressings for decay prevention, but want more proof. They are open-minded. Some have stopped using dressings; others are still using thinner coats of the materials.

Group III is made up of arborists who will not change their minds about wound dressings, or any other tree care practice, no matter what is said, done, or printed. Some members of this group manufacture wound dressings for profit.

Others have just grown up" with wound dressings and consider them a hallmark of professionalism. This is not bad, so long as the materials are not being sold or applied with the implication that they will prevent decay.

It is unrealistic to think that the use of wound dressings will ever cease; the search will continue for the perfect dressing. The increasing variety of new chemicals and the lure of easy profit encourage constant testing. The problem is that the emphasis is on the materials and not the tree, or profit first and tree second. The purposes of this paper are to present some additional data from wound dressing experiments to help Group 11, and to discuss new directions for helping trees, especially for Group 1. We respectfully recognize Group III, so long as they are professionals, but we will not try to convince them that wound dressings do not stop decay.

Materials and Methods

During the 1970s, several wound treatment studies were conducted near Barlett and West Thornton, New Hampshire, and Alfred, Maine. The studies were similar in general design, but there were some specific differences. Trees were wounded - with drill holes, ax cuts, or chisel wounds - some material was applied immediately after wounding (controls received no materials), the trees were cut after different periods of time, the wounds were dissected, closure was measured as width of open wound after periods of months to 7 years, microorganisms were isolated. and columns of discolored and decayed wood were measured. Tree species were red maple, Acer rubrum L., red oak, Quercus rubra L., white oak, Q. alba L., beech, Fagus grandifolia Ehrh.,

The use of trade. firm or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute endorsement or approval by the U.S. Department of Agriculture, or the U S. Forest Service.

New emphasis must be focused on the tree. If trees are well understood, then the ways-to help them stay healthy will also be understood (Shigo 1982b). Ignorance is our main problem. Understanding is the answer. We should not rely on medicines and wound dressings to correct problems we create. It is not so important to start new practices as it is to STOP many old practices that do more harm than good. If adjustments can be made in many tree care practices, then- there will be no need for dressings. For example, branch pruning has been a major tree treatment for centuries. The recommendation for 400 years has been to cut branches as close as possible to the joining stem, and then paint (Von Mayer-Wegelin 1936). If such cuts are made, the tree will be injured so seriously that even if a magic dressing were known, it would not help. If pruning cuts are made properly (Shigo 1982a), there is no need for a dressing. If cuts are made improperly, dressings will not help.

In the end, arborists of Group I will continue to make adjustments based on new information. Group II will consider the new information and begin to make some adjustments. And, Group III will not understand what is happening because they will be out painting wounds.